One of the major requirements which every cellular network operator faces is to ensure that the network is operating to its maximum efficiency. As a result, cellular network optimization is a major feature of many modern cellular networks.
In order to guarantee the best possible performance to the cellular network subscribers, the network is periodically optimized so that its resources can be more effectively utilized within the core network and/or the Radio Access Network.
Automatic Radio Access Network (“RAN”) management is not a matter of choice any more. Without it, modern radio networks would not be able to cope with their rapidly changing commercial environment, whose characteristics include:                Data usage is exploding while ARPU remains flat —forcing operators to drive down cost per bit in order to protect their margin profits;        Traffic patterns have become dynamic and unpredictable—making static optimization practices practically obsolete;        Traffic increasingly moves indoors—away from the coverage of macro networks;        The proliferation of new forms of base stations (small cells, Wi-Fi) opens an opportunity to drive costs down by commoditizing RAN equipment        
These trends lead to the creation of complex multi-layer, multi-vendor networks, mixing UMTS, LTE, macro, small cells and WiFi all together. Their users, nevertheless, expect a unified experience wherever they are, whatever service they are using. Only a network that is automatic and self-optimizing can handle this complexity and dynamical conditions. From this perspective, it is clear that a multi-technology SON is a key requirement, as it allows the network to match the best access method for every usage scenario. It is also clear why SON'a multi-vendor capability is not optional but an essence for the modern mobile topology.
The Self-Organizing Network (hereinafter “SON”) is an automation technology designed to make the planning, configuration, management, optimization and healing of mobile radio access networks simpler and faster. SON functionality and behavior has been defined and specified in generally accepted mobile industry recommendations produced by organizations such as 3GPP (3rd Generation Partnership Project) and the NGMN (Next Generation Mobile Networks).
Various technologies ar making use of SON features among which are WiFi, femto cells, Long Term Evolution (LTE) as well as older radio access technologies such as Universal Mobile Telecommunications System (UMTS). Newly added base stations should be self-configured in line with a ‘plug-and-play’ paradigm, while all operational base stations will regularly self-optimize parameters and algorithmic behavior in response to observed network performance and radio conditions.
In the past, the research work on SON for wireless networks has been focused mainly on stand-alone functions. However, with the increasing number of SON functionalities being implemented in the networks, the likelihood of conflicts arising during operations (i.e. while carrying out individual SON functions) also increases.
Therefore, a SON coordination is required in order to detect potential conflicts, avoid them by adequately harmonizing the policies and targets of SON functions, automatically resolve conflicts if and when they occur, and provide a single interface towards the operator regarding policies and targets setting, as well as SON system feedback.
One attempt to provide a solution to the above problems is described in “SON Coordinator—SOCRATES Approach” by Lars Christoph Schmelz, of Nokia Siemens Networks Oct. 20, 2010. However, the solution described in that publication is not completely satisfactory and does not provide adequate solution to various conflicts that arise while carrying out certain SON functions.